DC powered surgical handpieces have been commercially available for a number of years. These include battery operated surgical handpieces in the form of a self-contained handpiece incorporating a rechargeable battery. The assignee of the present invention has produced battery carrying handpieces of this type, including drills, reamers and saws, such as sagittal and reciprocating saws.
The present applicant has found that it is possible to improve over prior DC powered handpieces, particularly battery handpieces, in several respects.
For example, the present applicant has found that it is important to provide a control which is not only capable of providing the usual forward/reverse and variable speed control functions, but which can also be made physically compact so as to take minimal space in the handpiece and be conveniently located in the handpiece while not interfering with the balance of the handpiece and the ability of the handpiece to fit comfortably in the hand of prospective users.
Applicant has found it possible to achieve a desired motor power capability while limiting the peak current draw on the battery and thereby avoiding possible battery damage or control circuit damage and permitting a relatively compact battery to be used while, at the same time, limiting peak current in the motor windings, so as to allow the use of lower resistance windings and thereby increase efficiency in electric power usage across the entire power spectrum of the tool. By the same token, the motor can be made more compact while reducing the danger of motor overheating.
The present applicant has also provided for substantially instantaneous stoppage of motor rotation upon operator release of the trigger, to avoid the tendency of the motor to keep rotating for several turns, due to its own momentum, after trigger release. More particularly, applicant has recognized that one of the reasons that a surgeon may release the trigger of a rotary handpiece is that the bit, e.g. a rotary cutter, has accidentally become ensnarled in soft tissue. If the bit is allowed to continue rotation after the trigger is released, it will tend to start winding up such soft tissue with risk of injury to the surgical patient. The present applicant has found that dynamic braking, to avoid this problem, can be accomplished compactly and with few circuit components so as to minimize cost and assist in providing a compact, comfortably handed surgical handpiece.
Further objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the following description and inspecting the accompanying drawings.